Fiber optic connectors are used in equipment that is subject to wide temperature variations which can be from -40.degree. C. to 85.degree. C., especially in telecommunication and data transmission equipment. The fiber optic connectors will expand and contract under these temperatures. If a fluid is used in the connectors, the fluid under elevated temperatures will be forced away from the interface between ferrule members of the connector and will not return under lower temperatures because of the connector structure. The front ends of the connectors also need room to expand under elevated temperatures to prevent damage from occurring to the ends of the fiber optic transmission members. This is necessary even if no fluid is used.